// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <openssl/err.h>
#include <openssl/evp.h>
#include <string.h>

#include <memory>

#include "net/quic/crypto/aead_base_encrypter.h"
#include "net/quic/quic_flags.h"
#include "net/quic/quic_utils.h"

using base::StringPiece;

namespace net {

namespace {

    // The maximum size in bytes of the nonce, including 8 bytes of sequence number.
    // ChaCha20 uses only the 8 byte sequence number and AES-GCM uses 12 bytes.
    const size_t kMaxNonceSize = 12;

    // In debug builds only, log OpenSSL error stack. Then clear OpenSSL error
    // stack.
    void DLogOpenSslErrors()
    {
#ifdef NDEBUG
        while (ERR_get_error()) {
        }
#else
        while (unsigned long error = ERR_get_error()) {
            char buf[120];
            ERR_error_string_n(error, buf, arraysize(buf));
            DLOG(ERROR) << "OpenSSL error: " << buf;
        }
#endif
    }

} // namespace

AeadBaseEncrypter::AeadBaseEncrypter(const EVP_AEAD* aead_alg,
    size_t key_size,
    size_t auth_tag_size,
    size_t nonce_prefix_size)
    : aead_alg_(aead_alg)
    , key_size_(key_size)
    , auth_tag_size_(auth_tag_size)
    , nonce_prefix_size_(nonce_prefix_size)
{
    DCHECK_LE(key_size_, sizeof(key_));
    DCHECK_LE(nonce_prefix_size_, sizeof(nonce_prefix_));
    DCHECK_GE(kMaxNonceSize, nonce_prefix_size_);
}

AeadBaseEncrypter::~AeadBaseEncrypter() { }

bool AeadBaseEncrypter::SetKey(StringPiece key)
{
    DCHECK_EQ(key.size(), key_size_);
    if (key.size() != key_size_) {
        return false;
    }
    memcpy(key_, key.data(), key.size());

    EVP_AEAD_CTX_cleanup(ctx_.get());

    if (!EVP_AEAD_CTX_init(ctx_.get(), aead_alg_, key_, key_size_, auth_tag_size_,
            nullptr)) {
        DLogOpenSslErrors();
        return false;
    }

    return true;
}

bool AeadBaseEncrypter::SetNoncePrefix(StringPiece nonce_prefix)
{
    DCHECK_EQ(nonce_prefix.size(), nonce_prefix_size_);
    if (nonce_prefix.size() != nonce_prefix_size_) {
        return false;
    }
    memcpy(nonce_prefix_, nonce_prefix.data(), nonce_prefix.size());
    return true;
}

bool AeadBaseEncrypter::Encrypt(StringPiece nonce,
    StringPiece associated_data,
    StringPiece plaintext,
    unsigned char* output)
{
    if (nonce.size() != nonce_prefix_size_ + sizeof(QuicPacketNumber)) {
        return false;
    }

    size_t ciphertext_len;
    if (!EVP_AEAD_CTX_seal(
            ctx_.get(), output, &ciphertext_len,
            plaintext.size() + auth_tag_size_,
            reinterpret_cast<const uint8_t*>(nonce.data()), nonce.size(),
            reinterpret_cast<const uint8_t*>(plaintext.data()), plaintext.size(),
            reinterpret_cast<const uint8_t*>(associated_data.data()),
            associated_data.size())) {
        DLogOpenSslErrors();
        return false;
    }

    return true;
}

bool AeadBaseEncrypter::EncryptPacket(QuicPathId path_id,
    QuicPacketNumber packet_number,
    StringPiece associated_data,
    StringPiece plaintext,
    char* output,
    size_t* output_length,
    size_t max_output_length)
{
    size_t ciphertext_size = GetCiphertextSize(plaintext.length());
    if (max_output_length < ciphertext_size) {
        return false;
    }
    // TODO(ianswett): Introduce a check to ensure that we don't encrypt with the
    // same packet number twice.
    const size_t nonce_size = nonce_prefix_size_ + sizeof(packet_number);
    ALIGNAS(4)
    char nonce_buffer[kMaxNonceSize];
    memcpy(nonce_buffer, nonce_prefix_, nonce_prefix_size_);
    uint64_t path_id_packet_number = QuicUtils::PackPathIdAndPacketNumber(path_id, packet_number);
    memcpy(nonce_buffer + nonce_prefix_size_, &path_id_packet_number,
        sizeof(path_id_packet_number));

    if (!Encrypt(StringPiece(nonce_buffer, nonce_size), associated_data,
            plaintext, reinterpret_cast<unsigned char*>(output))) {
        return false;
    }
    *output_length = ciphertext_size;
    return true;
}

size_t AeadBaseEncrypter::GetKeySize() const
{
    return key_size_;
}

size_t AeadBaseEncrypter::GetNoncePrefixSize() const
{
    return nonce_prefix_size_;
}

size_t AeadBaseEncrypter::GetMaxPlaintextSize(size_t ciphertext_size) const
{
    return ciphertext_size - auth_tag_size_;
}

size_t AeadBaseEncrypter::GetCiphertextSize(size_t plaintext_size) const
{
    return plaintext_size + auth_tag_size_;
}

StringPiece AeadBaseEncrypter::GetKey() const
{
    return StringPiece(reinterpret_cast<const char*>(key_), key_size_);
}

StringPiece AeadBaseEncrypter::GetNoncePrefix() const
{
    if (nonce_prefix_size_ == 0) {
        return StringPiece();
    }
    return StringPiece(reinterpret_cast<const char*>(nonce_prefix_),
        nonce_prefix_size_);
}

} // namespace net
